This symposium follows two successful symposia held in 1969 and 1976. The major objective of this 3rd symposium is to present the most up-to-date concepts of internal dosimetry techniques. Dosimetry experts will be invited to present various facets of the problem, exchange points of view, and define major disagreements that may exist. We expect the conference to generate fruitful pathways for resolving some of the continuing questions on dosimetry and obtaining the biological information needed to improve radiation dose estimates. Topics will include radiopharmaceutical kinetic and retention data from patients, animals, and human volunteers; data collection methods; data extrapolation and analyses of biologic data. An important goal is to provide a reference volume that will serve as a resource for nuclear medicine practitioners and clinical investigators.